The invention relates to a hydraulic cylinder unit, specifically a hydraulic cylinder unit with a cylinder tube having an inner surface with a piston that is guided thereon and that has an outer surface, with a piston rod joined thereto whose rod surface is guided on a cylinder head that closes the rod-side cylinder space, with at least one rod seal arranged therein that seals the piston rod-side cylinder space from the area of the cylinder unit between the rod surface and the cylinder head by means of a rotationally symmetrical inner seal surface, and with at least one piston seal arranged in the piston that seals the piston-rod side cylinder space and the cylinder space formed by the cylinder floor and the piston between the cylinder space inner surface and the outer surface of the piston by means of a rotationally symmetrical outer seal surface.
Especially low-friction cylinder units are of interest for various purposes. Among these are cylinders for suspension and steering functions, or working cylinders subject to high demands in terms of sensitivity and positionability. The effect of increased friction is a poor ratio of effective force, that is working force of the cylinder, to theoretical pressure force. Among other things, this leads to the fact that the cylinder must be designed larger than theoretically necessary in order to provide adequate effective force.
In suspension cylinders, the frictional force acts like additional damping. However, the greater the basic damping of the cylinder itself, the lower the portion that can be effectively influenced in the control. However, it is precisely the option for influencing damping that is the basis for a modem, active suspension and damping system.
In addition to relatively high friction, the ratio of static friction to sliding friction is also of interest because major differences between the two values can lead to undesired oscillations or vibrations (so-called stick/slip effect).
Finally, unsatisfactory friction values and relatively wide variance of known hydraulic cylinder units in series are also disadvantageous.
The object of the invention is therefore to design a hydraulic cylinder unit such that it is particularly low in friction.